Voltage and load independent flasher unit

ABSTRACT

A flasher unit comprising an indirectly heated shunt flasher in combination with a voltage-regulating network comprising a resistor and a zener diode connected in series between the terminals of the flasher unit, with the zener diode being connected in parallel with the heater element of the flasher.

United States Patent Siiberg 1 51 Dec. 5, 1972 1541 VOLTAGE AND LOAD INDEPENDENT 3,246,181 4/1966 Bleiweiss...'. .307/132 T L SHER NIT F U OTHER PUBLICATIONS [72] Inventor: Hemming G. Siiberg, Summ1t, NJ. v

Toback, Stab1l1ze Tube Heater Voltages, Electronic [73] Ass1gnee: Wagner Electric Corporation d i 1953, 4

Nibler, Zener Diodes, The review of Scientific In- {22] Flled' 1971 struments, Oct. 1961, p. 1143.

[2]] App]. No: 106,967

Primary Examiner-R0bert K. Schaefer 1 Assistant Examiner-William J. Smith [52] US. Cl. ..307/l3 2 T, 307/318, 340/81 51 1111.01. .B60q 1/46, HOlh 37/00 momey Lucas [58] Field of Search ..340/81, 331, 342; 317/132; [57] ABSTRACT 323/222, 8 A flasher unit compnsmg an 1nd1rectly heated shunt 1 flasher in combination with a voltage-regulating net- [561' References Cited work comprising a resistor and a zener diode connected in series between the terminals of the flasher UNITED STATES PATENTS unit, with the zener diode being connected in parallel 3 243 773 3,1966 L h with the heater element of the flasher. BIC senrlng 3,080,464 3/1963 Kurz ..337ll 39' 5 Claims, 2 Drawing Figures VOLTAGE AND LOAD INDEPENDENT FLASIIER UNIT The present invention relates to a flasher unit which is independent of applied voltage and load current within the wide ranges-encountered in automotive applications. In this unit, an indirectly heated shut flasher is combined with a voltage regulating network which serves to maintain a steady value of voltage across the heater element of the flasher whenthe flasher contacts are open.

A better understanding of the present invention may be had by reference to the accompanying drawings, of

. which:

FIG. 1 is a schematic diagram of the flasher unit shown as'it would be connected in anautomotive circuit; and

FIG. 2 is an isometricview of'a travelling mandrel mounted on a thermally expansible pull ribbon, with a heater element disposed about the travelling mandrel.

Referringnow specifically to FIG. 1, the flasher unit comprises an indirectly heated shunt flasher 12 which includes a mechanically biased member such as a snap blade 14, a thermally expansible pull member (ribbon or'wire) 16 attached to the low-resistance snap blade 14, a heater element 18 wound about the pull member 16, a moveable contact 20 mounted on the pull ribbon-snap blade .subassembly, and a fixed contact 22 mounted in co-operative make-and-break relationshipwith moveable contact 20. Theflasher unit 10 furthercomprises a voltage-regulating network formed by resistance 24 and zener diode 26 connected in series between terminals 28 and 30, and between fixed contact 22 and the low-resistance snap blade 14. The flasher 12 maybe of any suitable type, including, for

example, the flasher disclosed in U.S. Pat. No.

path from the voltage source V through terminal 28, fixed contact 22, moveable contact 20, snap blade 14, terminal 30, switch S, and load L to ground. The voltage regulating network is thus shunted and heating current no longer passes through heater element 18. Thus, the load L is fully energized. Cooling of pull member 16 begins upon the closing of contacts 20, 22 and will eventually cause the pull member 16 to contract sufficiently to overcome the mechanical bias in snap blade 14 to cause the contacts 20, 22-to snap open. The load L is again effectively de-energized, and the aforementioned cycle repeats itself so long as switch S remains closed. I

Since the zener diode 26 is selected to have a lower zener voltage than the anticipated minimum supply voltage, the current through the heater will be constant whenever the contacts 20, 22 are open, resulting in the flasher unit 10 having a constant OFF time, i.e., the time between the initiation of energization of heater 18 and the closing of contacts 20, 22. Since it is an in-, herent characteristic of shunt flashers that the ON time 7 is constant, being a function of the cooling time of the pull member, the flasher unit 10 will also have ya constant on time regardless of the applied voltage. Consequently, the ratio of the flasher unit 10 will be constant. Also, since the shunt flasher 12 is insensitive to variations in load current, the flasher unit'l0 will be in- U.S. Pat. No. 3,349,205 issued on Oct. 24, 1967 upon an application filed by Sidney Taylor, or the indirectly heated shunt version of the flasher disclosed in U.S. Pat. No. 3,470,515 issued on Sept. 30, 1969 upon an application filed by Hemming G. Siiberg. For a 12 volt electrical system, the zener diode 26 preferably has a zener breakdown voltage'of 8.2 volts and a power dissipation-capability of 1 watt. Resistor 24 preferably has a value of 15 ohms and a power dissipation capability of 0.5 watt. The expansible pull member 16 is preferably NICHROME ribbon having a width of 0.05 inch and a thickness of 0.0025 inch. The heater element 18 is preferably insulated NlCI-IROME wire of 0.002 inch diameter and having a resistance of approximately 60 ohms.

The flasher unit 10, when connected in a circuit as shown in FIG. 1, operates as follows:

When the switch S is closed, a high-impedance current path is closed from the source of DC voltage V through terminal 28, resistance 24, zener diode 26, termine! 30, switch S, and load L to ground. If load L is an incandescent lamp, the magnitude of the current flowing therethrough will be well below the value required to render the lamp incandescent. The steady voltage generated across zener diode 26 will be applied across heater element 18, which upon heating will cause pull member 16 to expand. The mechanical bias of snap blade 14 will consequently cause contacts 20 and 22 to snap closed, thereby closing a low-impedance current dependent of load current.

Referring now specifically to FIG. 2, a travelling mandrel 32 is shown mounted on a pull ribbon 34 by means of welds at points 36 and 38, with a heater element 40 wound around the travelling mandrel 32. The mechanically biased member 42 shown in phantom is disclosed in the aforementioned U.S. Pat. No. 3,470,515 issued on Sept. 30, 1969 upon an application filed by Hemming G. Siiberg. In thepreferred embodiment of this feature, the pull ribbon 34 is stainless steel, having a width of 0.05 inches and a thickness of 0.003 inches. The travelling mandrel 32 is of like composition and dimensions, and is offset by about 0.015 inches from the pull ribbon 34. Theheater wire 40 wrapped around the travelling mandrel 32, when supplied with heating current, transfers heat to the pull ribbon34 by conduction through the travelling mandrel 32 via the points of connections 36 and 38. Heat transfer may also be effected by convection.

This arrangement has been found to afford several advantages. First, a faster cooling rate of the pull ribbon can be achieved, resulting in a more uniform OFF time. Second, the flasher unit is less susceptible to ambient temperature changes, resulting in a unit which is more drift-free without any reduction in cooling rate. Third, in certain types of flashers, for example the indirectly heated version of the flasher disclosed in U.S. Pat. No. 3,470,515 issued on Sept. 30, i969 upon an application filed by Hemming G. Siiberg, or the indirectly heated version of the flasher disclosed in U.S.

Pat. No. 3,218,4l5 issued on Nov. 16, 1965 upon an application filed by Henry Voorman, Jr.,'mechanical interference which would occur between heater element and snap blade if the heater element were wound around the expansible pull member is eliminated.

The advantages of the present invention, as well as certain changes and modifications of the disclosed embodiment thereof, will be readily apparent to those skilled in the art. It is the applicants intention to cover all those changes and modifications which could be made to the embodiment of the invention herein chosen for the purposes of the disclosure without departing from the spirit and scope of the invention.

What is claimed is:

l. A flasher unit comprising:

l. thermo-responsive flasher means including a heater element and a pair of contacts disposed in cooperative make-and-break relationship;

2. voltage regulating means operative when said heater element is energized to maintain a constant voltage across said heater element; and

3. support means including first and second terminal means operative to support said thermo-responsiveflasher and to enable connection of said flasher and said voltage regulating means to external circuitry.

2. The flasher unit according to claim 1 wherein said thermo-responsive flasher is an indirectly heated shunt flasher having normally open contacts.

3. The flasher unit according to claim 1 wherein said voltage regulating means comprises a resistance and a zener diode connected in series between said first and second terminal means, with said heater element being connected across said zener diode.

4. the flasher unit according to claim 1 wherein said thermo-responsive flasher includes an expansible pull ribbon and a travelling mandrel mounted thereon, said heater element being wound around said travelling mandrel.

5. A flasher comprising: unit 1. a shunt flasher including first and second terminals, a snap blade-expansible pull member subassembly, a moveable contact mounted on said subassembly, a fixed contact mounted in cooperative make-and-break relationship with said moveable contact, and a heater element operative to heat said expansible pull member; and

2. a voltage regulating network comprising a resistance and a zener diode connected in series between said first and second terminals and between said fixed contact and said snap blade, said zener diode being connected in parallel with said heater element.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORREC'HN Patent No. 3,7 5,5 vDated December 5, 1972 Inventor(s) Hamming G. Siiberg It is certified that eri'or apoears in the above-identified patent and that said Letters Patentare here'by corrected as shown below:

Col, l, Line 6: "shu t should read shunt- Col, 4, Claim 4, Line 1: l "the" should read --The -w Col. 4, Claim 5, Lir ze I l: "A flasher comprising unit" should read --A flasher unit comprising-- Signed and sealed this 1&1: day of May 1973.

. (SEAL) Attest:

" EDWARD M. FLETCHERJR. I v ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM P0-1050 (10-69) uscoMM-Dc 60376-P69 a- U.S. GOVERNMENT PRINTING OFFICE I969 O3S6334 

1. A flasher unit comprising:
 1. thermo-responsive flasher means including a heater element and a pair of contacts disposed in cooperative make-and-break relationship;
 2. voltage regulating means operative when said heater element is energized to maintain a constant voltage across said heater element; and
 3. support means including first and second terminal means operative to support said thermo-responsive flasher and to enable connection of said flasher and said voltage regulating means to external circuitry.
 2. voltage regulating means operative when said heater element is energized to maintain a constant voltage across said heater element; and
 2. The flasher unit according to claim 1 wherein said thermo-responsive flasher is an indirectly heated shunt flasher having normally open contacts.
 2. a voltage regulating network comprising a resistance and a zener diode connected in series between said first and second terminals and between said fixed contact and said snap blade, said zener diode being connected in parallel with said heater element.
 3. The flasher unit according to claim 1 wherein said voltage regulating means comprises a resistance and a zener diode connected in series between said first and second terminal means, with said heater element being connected across said zener diode.
 3. support means including first and second terminal means operative to support said thermo-responsive flasher and to enable connection of said flasher and said voltage regulating means to external circuitry.
 4. the flasher unit according to claim 1 wherein said thermo-responsive flasher includes an expansible pull ribbon and a travelling mandrel mounted thereon, said heater element being wound around said travelling mandrel.
 5. A flasher comprising: unit 